A mysterious Internet outage left an estimated 200 million Internet users in China unable to access several websites for about eight hours on Tuesday. Now Chinese officials are pointing to a cyberattack, which some have come to believe originated in the U.S. with a controversial religious group, the Falun Gong.

Several reports on that day stated that when attempting to access China’s biggest websites, with domain names such as .com, .org or .net, users were redirected to a site for Dynamic Internet Technology, a company that sells anti-censorship services, has publicly opposed censorship in China, and is run by a Falun Gong follower, Bill Xia.

The Chinese government condemns the movement, and its followers are suppressed in mainland China. In 1999 the Communist Party outlawed the group as a “heretical organization” that was a threat to the party and to social stability. All news or conversation about the Falun Gong group is strictly taboo, comparable to talking about the 1989 Tiananmen Square protests. As a result, many of the Falun Gong’s followers are found overseas, namely in the U.S.

Though the official report from Chinese officials suggests an external hack was responsible, it’s still unclear if the religious group had anything to do with taking down two-thirds of China’s Internet access. “According to an analysis of available data, the center has preliminarily concluded that this incident was caused by a cyberattack,” the National Computer Network Emergency Response Center said in a statement. “The source of the attack is under further investigation.”

During a news briefing, Foreign Ministry spokeswoman Qin Gang recognized the link to Bill Xia, but was cautious to point the finger. “I don’t know who did this or where it came from, but what I want to point out is this reminds us once again that maintaining security needs strengthened international cooperation,” Qin said. “This again shows that China is a victim of hacking.”

In an interview with CBS News, Xia said he is not convinced that the outage was the doing of an external source, let alone the spiritual group. “It’s unclear whether the situation was the work of savvy hackers or the result of some kind of glitch in the Great Firewall.” Xiao Qiang, an expert on Chinese Internet controls based at UC Berkeley, found similar results. “Our investigation shows very clearly that the domain name service exclusion happened at servers inside China,” Xiao told Reuters. “It all points to the Great Firewall. How it happened or why that happened, we’re not sure.”